Python - neat way of creating multiple objects?

Question

I'm fairly new to Python and I have a question about a neat way of creating multiple objects with different properties. At the moment I am having to specifically create each one like this:

object1 = MyClass(property=foo,property2=bar)
object1.DoStuff(variable = foobar)

object2 = MyClass(property=foo,property2=bar2)
object2.DoStuff(variable = foobar)

object3 = MyClass(property=foo,property2=bar3)
object3.DoStuff(variable = foobar)

My problem is that I want to create dozens of objects in this way and having to manually create each one like this seems like very bad programming. Is there a better way to create multiple objects with slightly different properties?

I guess what I want to do is something like:

list = [prop1, prop2, prop3, prop4, prop5]
while i < len(list)
    object_i = MyClass(property=foo,property2=list[i])
    object_i.DoStuff(variable = foobar)
    i+=1

And have this create 5 objects named object_1, object_2, etc etc

Is this possible?

You should keep data (including indices) out of your variable names. — Sven Marnach
– Sven Marnach, Commented Apr 12, 2012 at 15:27
@vartec No, I'm long past the homework stage...just new to programming! — FakeDIY
– FakeDIY, Commented Apr 12, 2012 at 15:34

Sven Marnach · Accepted Answer · 2012-04-12 15:29:53Z

12

If you have objects with the names object_1, object_2 etc. and want to perform common operations on all these objects, this is a clear sign that you should actually be using a list objects, and use loops to perform the common operations.

props = <some list here>
objects = [MyClass(property=foo, property2=prop) for prop in props]
for obj in objects:
    obj.do_stuff(variable=foobar)

answered Apr 12, 2012 at 15:29

Sven Marnach

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1 Comment

FakeDIY Over a year ago

Thanks. It seems really obvious when you see it! :-)

covertCoder · Accepted Answer · 2012-04-12 15:45:20Z

Another way of going about this could be using more meaningful object definitions with the help of a dictionary. Sven Marnach's solution works well if all you care about is object_1, object_2, etc. but what if your objects actually have individual importance later? Referencing them will become unintuitive and you'll get lost pretty fast. Here's some sample code to help you out in this regard:

objectNames = ("foo", "bar", "cat", "mouse")
objectDictionary = {}
for name in objectNames:
    objectDictionary[name] = MyClass(property=foo,property2=bar)

for obj in objectDictionary.itervalues():
    obj.DoStuff(variable = foobar)

If you want a specific instance to do something different from the others, this solution makes this easy:

objectDictionary["bar"].DoSomethingElse(variable = cat)

Ignacio Vazquez-Abrams · Accepted Answer · 2012-04-12 15:27:14Z

2

Use tuple unpacking along with a list comprehension.

object_1, object_2, ... = [MyClass(property=foo, property2=x) for x in (bar,
  bar2, ...)]

answered Apr 12, 2012 at 15:27

Ignacio Vazquez-Abrams

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2 Comments

FakeDIY Over a year ago

Thanks. That makes sense. How do you then do object_1.DoStuff, object_2.DoStuff, etc?

Ignacio Vazquez-Abrams Over a year ago

Sure. But if you're going to do it to every single object then you should put them in a list as Sven says.

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